1. Field of the Invention
The present invention relates to a speed correcting device for use in a speed command system of an apparatus having a movable machine part which is driven at a speed corresponding to a speed command value and, more particulary, to a speed correcting device which permits driving of the movable machine part at a speed accurately corresponding to the speed command value.
2. Description of the Prior Art
In a machine tool or the like, a movable machine part is driven at a speed corresponding to a speed command value received from a tracer controller, numerical controller or the like. But a defect in this method is that the driving speed of the movable machine part differs from the speed command value due to the influence of an offset voltage in the speed command system aging of an element used changing its characteristics. To avoid this, it is a general practice in the prior art to provide a variable resistor for speed control in the speed command system and to manually vary the resistance of the variable resistor, thereby bringing the actual moving speed of the movable machine part into agreement with the speed command value. But this method not only increases the work of the operator but also lacks accuracy because of the manual adjustment of the variable resistor.